MartinLogan ESL speakers highest current draw is in the highest frequencies where there is usually minimal recorded sound which make them easier to drive than expected. Currently driving my ML-11a's with a Mcintosh ma352 with no issues.
Electrostatics and tubes
I am looking to get some new to me speakers, I've been looking at options and would really like to try a set of planars "electrostatics". I have read or heard somewhere that as far as speakers go they tend to be inefficient (85 to 89) vs.90+(db) on the Klipsch or Dali's I've been tossing around as a standard speaker option. I guess my question is would I need to worry about any over heating issues. I plan on using plenty of power with a set of VTA, M-125's to power them. I am looking at a lower budget set maybe Martin Logan ESL 9's or Magnepan 2.7i . Just wondering I would hate to over heat a few hundred dollars worth of tubes if I don't need to. ¯\_(ツ)_/¯ don't roast me to bad I cry easy 
thanks.